The Suzuki rider dropped in a 2m04.599s lap, edging out the reigning world champion by just 0.056 of a second.

“I have a good feeling at this circuit, and a good feeling with the bike,” Iannone said.

“We hope to improve tomorrow, and I believe that anything is possible because I feel positive and ready to fight for the top.”

Marquez remains the rider to beat this weekend.

His unbeaten record at COTA — and his streak of 12 consecutive race wins on American soil dating back to his first Moto2 race at Indianapolis in 2011 — overshadows both the lingering controversy over his clash with Rossi in Argentina and a crash at Turn 11 midway through the second session.

The factory Yamahas were next, Maverick Vinales ahead of Rossi, with last-start winner Cal Crutchlow rounding out the top five.

But the big talking point of the day was the dusty state of the Circuit of The Americas.

The circuit’s tarmac underwent diamond grinding in recent weeks to try and eliminate some of the bumps, but left the track coated with enough dust that bikes were throwing up rooster tails of grit during the early parts of practice.

“It’s so bad down that back straight, it’s ridiculous,” Jack Miller told motorsport.com after finishing the day 14th.

“I came out of there on the first lap behind Dovi and I actually buttoned off (the throttle) because it was getting roosted, and it was like big old rocks hitting me at 300km/h ...

“They felt like bullets. I wasn’t too keen on that.

“We’ve broken a windscreen already with the rocks and the dust, I’m gonna put some drops in my eye now because I hate dust!”

Jorge Lorenzo hit back after a difficult start to the season to be the best of the Ducatis in seventh, 0.160s ahead of Andrea Dovizioso, with Aleix Espargaro putting his Aprilia ninth to make five manufacturers in the top 10.

Rounding out that top 10 was Dani Pedrosa, still nursing a broken wrist after his Lap 1 highside out of the GP of Argentina.

“I gave maximum effort in order to understand if there’s any reason to race on Sunday,” he said.

“This morning I felt quite a lot of pain, but I just tried to feel what I could do on the bike. My pace wasn’t so good, so I tried to put myself in a better position this afternoon, and I’m very pleased with the outcome.

“Now we have to try and control the swelling ahead of tomorrow’s action.”

Rain is forecast for early on Saturday which could prevent Miller or any other riders from bumping their way into the top 10 combined practice times, setting the fields for Q1 and Q2.